Network, generic (extended)

U3557 Hydrogen Tank C Valve Enable Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3557 is stored for a fault in the enable circuit of the tank C valve, the third tank of three-tank vehicles. Permission to open is not tied to driving alone: a Honda patent describes the cutoff valve being open with the ignition off, for example when the stack keeps operating after shutdown, so collision detection stays powered in that state and a cutoff relay can still close the valve. The enable path therefore has to work when the car is parked, and faults may surface after switch-off. FMVSS 307 asks for valve closure within 5 seconds of any crash. No manufacturer documents U3557. Expect tank C to stay shut, a warning and less range. If U3551 and U3554 are also stored, look for a supply common to all valves.

Likely causes

Cutoff or enable relay for valve C faulty
Fuse or common valve supply interrupted
Enable line to tank C damaged

Symptoms

  • Hydrogen system warning, possibly right after switch-off or at start
  • Reduced range

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–1,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

h2 tank c valve enablesafety circuit

Related codes

U3556U3558U3551U3554

References: patents.google.com, law.cornell.edu.